The wiring resin substrate is provided on its principal face with a number of pad-shaped electrodes to be used for mounting electronic parts such as an LSI or an IC chip thereon and on its other principal face with a number of terminal pad conductors (or electrodes) to be connected with a mother board and connection terminals (e.g., solder balls) disposed on the terminal pad conductors. The wiring resin substrate of this type is small-sized and increased in the connection terminal number (e.g., the ball number) so as to enhance the integration and density of the electronic parts such as the LSI, the IC chip or a chip capacitor to be mounted thereon.
This wiring resin substrate is generally provided, in its internal structure, with: a core substrate having a through hole conductor and a filling material in a through hole formed in an insulating substrate; a terminal pad conductor formed on the end face of the through hole for disposing a cover-shaped conductor portion, a resin layer and a connection terminal (e.g., solder balls); and a via conductor buried in the resin layer for bringing the through hole conductor and the terminal pad conductor into conduction. As background arts, JP-A-2000-91383, JP-A-10-341080, JP-A-2000-307220 (Paragraphs [0014] and [0015]), JP-A-2000-340951 (Paragraphs [0014] and [0015]) are known.